Peald-TiN Protective Coatings for Metallic Bipolar Plates of PEMFC

Abstract

Proton Exchange Membrane Fuel Cell (PEMFC) is an electrochemical device that convert the chemical energy of reactants directly to electrical energy. The water-based, acidic polymer membrane usually used as its electrolyte. Therefore, the bipolar plate, as one of the most important components in PEMFC system, is required to be high corrosion resistance in the acidic condition. Currently, researchers have tried to develop metallic bipolar plate using a stainless steel. In case of using stainless steel, a passivation or protective coatings layers should be applied to improve its stability in the harsh environment. However, the general intrinsic defects (columnar structures, pinholes, pores, discontinuities) in the protective films, which can greatly affect its high performance. Therefore, a passive thin film with low defects and stable property was needed to be developed. In this work, TiN thin films were deposited on 316L stainless steel as the protective layer by using plasma enhanced atomic layer deposition (PEALD). For comparison, tetrakis-dimethylamido-titanium (TDMAT) and titanium tetrachloride (TiCl4) were used as different Ti sources, respectively. The microstructure, chemical composition and the corrosion behavior of TiN protective layer deposited by different sources were investigated by 4-point probe, XRD, FESEM, AES and potentiodynamic polarization equipment. The SEM results showed that the uniform TiN protective layers were successfully deposited on the 316L stainless steel substrate by both two sources. and the FCC crystal structure was confirmed by the XRD analysis. In addition, the TDMAT-deposited TiN has lower the corrosion current density (Icorr) and higher corrosion potential (Ecorr) than those of TiCl4-deposited TiN, which could be inferred that the TDMAT-deposited TiN will have a higher corrosion resistance and protective efficiency during the fuel cell application.